


A Master's Onus

by On_And_Off_Writer



Category: Fate/Grand Order
Genre: Anal Fingering, Anal Sex, Blow Jobs, Come as Lube, Creampie, Everyone Is Gay, Hand Jobs, M/M, Porn, Rough Sex
Language: English
Status: In-Progress
Published: 2020-09-04
Updated: 2020-09-20
Packaged: 2021-03-06 16:06:53
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 2,752
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26271589
Author URL: https://archiveofourown.org/users/On_And_Off_Writer/pseuds/On_And_Off_Writer
Summary: At the start it was fine, just saving humanity and summoning servants to get their help, it wasn't that fine when he realised that every servant he summoned was male but when America ended and a new batch of servants where summoned, a certain servant made a move that changed everything.For the better.
Relationships: Cú Chulainn Alter | Berserker/Male Fujimaru Ritsuka, Fergus mac Róich | Saber/Male Fujimaru Ritsuka, Fujimaru Ritsuka/Everyone
Comments: 9
Kudos: 33





	1. The first time

**Author's Note:**

> For all intents and purposes Fujimaru is eighteen in this fic

It was a normal day in chaldea with the servants and staff in the cafeteria, the newest allies in Chaldea were eating in a table of alike servants.

The quartet of Celtic Servants are composed by Diarmuid, Fionn, Fergus and Cú alter, the latter nowhere to be seen, but the ones that were present are accompanied by the previously summoned celtic servants.

"I'm just saying, there are a _lot_ of men in this place ain't it?" Said Fergus, finishing his cup of rum, around them were servants from various places and time in history with one thing in common, they are all men.

"You are just saying that because you haven't gotten laid in a while" Said LancerCú

"Eh? That may be true but i know i am not the only one suffering, right Fionn? Don't tell me you don't miss the soft skin of a fair lady?" Said the Swordsman.

"While it is true i would appreciate the sight of more beautiful women, their absence does not disturb me much, besides aren't you satisfied with either gender?" The man kept eating fish as he dismissed fergus' complains.

"Yeah, if you are getting this anxious why don't you just take care of it yourself, like the rest of us" Commented CasCú.

"You know is not the same, i need to feel the tender soft skin or the abrasive heat of-".

"Come _on_! We are _eating_ old man!" Protested the younger version of Cú.

"Seconded" Came a voice from the kitchen and soon enough Emiya arrived, a scoul on his face "I am going to ask you to leave the cafeteria until you... _calm_ yourself".

"Ah yes, sorry i got carried away maybe i do need to calm myself" Fergus got out of the cafeteria and walked around the hallways of Chaldea, with umpure thoughts on his head.

* * *

It was when Fergus was getting to his room that he encountered his master on his combat suit

_'That tight combat suit really accentuates master's surprisingly fit body, his waist, his toned legs... his plump ass'._

"Coming from training Master?" Fergus tried to ignore his impulses and make a little chat with his new master.

"Yeah well, someone has to farm embers for you guys, besides Zhuge and Santa alter that is" Ritsuka scratched his cheek, now that Fergus gave his new master a good look he realized how soft his master's skin looked like, Fergus grabed his master hand feeling how soft it felt against his callous hands ""ehh sir Fergus?" Ritsuka was looking nervous, his face beet red.

"Ah sorry master, i am just feeling uneasy and you don't need to call me sir, Fergus is alright" Fergus let go of Ritsuka's hand

"And can i... help you?" Ritsuka lowered his gaze to the floor, his hand reaching for Fergus'.

Fergus was left agape, his new master had to have misunderstood him, he doesn't seem the type to do it with whomever asked.

"My room is just around the corner and Kiyohime is busy arguing with Elizabeth, plus she doesn't know i have come back from rayshifting" Ritsuka grabbed Fergus' hand and guided him through the halways of chaldea and stops in front of a door, Fergus asumes is his master's room.

"Let's not waste time, who knows when will a servant come bother us" entering the room and the door closing behind them Ritsuka gets out of his combat suit leaving his body naked with the exception of tight boxers that shows off his decent sized bulge. "Like what you see?" Ritsuka sat on the bed and grinned to the saber. 

"Very" The shirtless man couldn't help himself anymore and took his pants off, revealing his fundoshi. 

"How oddly japanese for a celtic warrior" Said Ritsuka, his hands slowly rising to make off the fundoshi before rising his head to see Fergus. 

"Well it's pretty comfortable but go on you can undo it" Soon enough the cloth dropped to the floor, Fergus' dick was awake but not hard yet. 

"How long does it get" Asks Ritsuka, his eyes concentrated on the semi hard dick in his hand.

"Last i cheked 18 centimeters" Said Fergus proudly as he watched Ritsuka's eyes widen at his answer.

"i've never... eight...well i'll... I'll start" Ritsuka's hands started pumping Fergus dick back and forth on their grip, each time the meat growing bigger and bigger until it reached the said size.

"Impressed?" Asked smugly Fergus. 

"Very" Ritsuka's attention didn't went away until he grinned "No wonder you are in the saber class" Said before liking the shaft.

"Willing, funny and cute to boot, you are already a better master than most i had" Fergus carresed Ritsuka's hair as he finally went in on Fergus' member.

Ritsuka bobbed his head up and down, his hands carresed his balls, trying his best to please Fergus, his servant.

"That's enough master, why don't you lie in bed and _i_ make you feel good" Fergus pished his master lightly on to his bed, his hands getting rid of the boxers and revealing a modest hard on wich was quickly griped by a rough hand, Ritsuka whimpered at the act. 

"How does it feel master?" The saber's hand started to handle the dick masterfully.

"Goo...ah... Good" Whimpered Ritsuka.

"Then this is going to feel better" Fergus took all of Ritsuka's dick on his mouth and started giving him a blowjob.

"Ahh... Fergus stop i... I am go..." Before he could finish he started cumming, cum that Fergus collected on his hand. 

"This is a lot huh? Do you not masturbate?" He asks.

"Too busy... I am sorry Fergus" Says Ritsuka.

"Why?"

"This was supposed to be your opportunity to let loose and... It was me who got most pleasure out of this" Finished Ritsuka.

"Oh don't worry master i think you needed this too and besides i am not done yet"

"Excuse me?" Asks Ritsuka as he feels something slimy reach his buttcheeks.

"I don't think you have lube so i am going to use this, alright?" Ritsuka let another whimper as he felt Fergus cum soaked finger making it's way insidd him. 

"Could you separate your legs?... Thanks, here comes the second finger" Fergus inserts his second finger and starts making a scissor like movement, stretching Ritsuka for his big dick. "Say master you are taking this in stride and you are clean too, did you..." 

"I... I practice with... with a dildo" Responds Ritsuka in between breaths. 

"So is this ok?" He asked stopping stretching his master and posicionating his tip on his master's entrance.

"Yes, p-please, gi-give it to me" Said Ritsuka as he grabbed his own legs over his head. 

"Your wishes are my command" Said Fergus before ramming all of his lenght inside his master, earning a loud gasp from his master, then he started getting in and out of him.

Ritsuka's gasp gradually turned into moans, his neglected dick got hard again and started bouncing, his eyes started to lose focus and going up to his skull.

During the next hour Fergus changed Ritsuka into various sex positions, never letting his dick get out of his master and letting his cum store insidd him.

By the end of it Ritsuka was on top of Fergus muscular body, panting and with a dick slowly getting out of him, letting all of Fergus' load to get out of his ass.

"Thanks master i really needed this, we should do this again sometime" Said Fergus, carefully getting his master on the bed instead of on top of him.

Ritsuka, tired as anyone would expect, only nodded, being fucked by a superhuman for an hour does that to anyone.

"Well i have to go, thanks again master, goodbye" those were the last words Ritsuka heard before drifting to sleep.

* * *

When Fergus got out of Ritsuka's room in the most inconspicuous way he could muster, he did not realize that a certain blue haired servant took notice of this.

"How interesting"


	2. Exploring new genres

**Summary for the Chapter:**

> Ritsuka's extra-activities were found out by quite the pair of servants.

Ritsuka was resting on his bed feeling horny as fuck, recounting the events just a pair of days ago with Fergus made him hard as rocks and not even masturbating helped. Plus every time that him and Fergus were in the same room he was undressing him with his gaze.

"Maybe it wasn't the best idea to let the big horny man fuck me" Ritsuka muttered, trying to ignore his dick.

"Now, now, master don't say such things just when we were interested" Turning around ritsuka found Hans dragging his labcoat and Shakespeare on his more light outfit with their pads and books respectively, both on the frame of his door.

"He-Hey guys what do you mean?" Said Ritsuka trying to hide his boner from the sight of the two casters.

"Don't bother trying to hide, it just makes it stand out more, jailbait" Hans said with a grin on his face.

"Ja-Jailbait? i'll have you know i am going to be nineteen in a few months and what about you?" He pointed a finger to Hans direction.

"What about me? i am not the one who seduced a servant known for being lustfull" Hans rebutted, Ritsuka didn't say anything else, lest it be used against him. "Now while i don't aprove of your actions, i can relate to the feeling of not being able to experience sexual relationships so i decided to give you an advice".

"An advice? from you? ok i am all ears, whatever you have to say i know it will be important" Ritsuka waited with starry eyes for Hans' advice, even Shakespeare seemed interested as to what kind of sexual advice would Hans, known virgin, give.

"Give up and get friendly with your hands"

"..."

"..."

"What?" At Ritsuka's commentary Shakespeare stopped containing and let out a boisterous laugh that echoed in the entire room, soon enough followed by Hans "Wha- What is so funny!?" soon enough the two casters stopped laughing.

"I'm sorry master, it's just that your facial expressions are perfect material for our next work" Said Shakespeare.

"And on that note i will tell you that i wasn't being completely honest, i know how painful it can be to want a meaningful relationship on a more... carnal... level, even wanting those relationships with men, only to fail in the end, so i figured i could help you, Shakespeare and i have been wanting to explore new genres, which means collecting more material for references" Explained Hans.

"Wait so that means-".

"That's right master, with your conscent i could use King's men to recreate scenes that you fantasize abo-".

"Do it" Ritsuka interrupted Shakespeare leading to Hans laughing at the interaction.

"Well, well, horny brat tell us what do you want to experience and we will take note" It passes well over half an hour for Ritsuka to explain what he wants. the pair of casters letting him to rest until the time is right.

* * *

Ritsuka was sleeping peacefully on his bed when he felt it.

At first it was a touch on his shoulder, he ignored it.

Then it was a touch on his back, he opened his eyes.

At last it was a carresing hand on his ass, he gasped but remained still, this was the beggining of the scene.

Soon his boxers were being taken down, first hearing the slap and then feeling it "Don't pretend to be asleep bitch".

The next slap made Ritsuka leave a yelp, he turned around to see who was his assailant.

The person, no, the group of people he found were all men with the chaldea staff uniform, their faces were somehow there but not there at the same time.

"Wha- what is th-"

"Shut it slut, did you think we wouldn't realiaze, you 'the last master of humanity' are fucking with the servants while we are breaking our backs mantaining Chaldea afloat" Ritsuka couldn't quite see their expressions but he could tell they were enraged.

"I- it was just one time i- i swear, besides Fergus was getting anxious"

"Anxious! So the next time he gets anxious are you going to bend over like the bitch you truly are?" Ritsuka opened his mouth to protest. "Shut it, we decided that if you could relief your needy ass then we could relief our needs here, with you, let's do this boys" The leader promptly took his pants off and with a wave of his hands two naked guys took Ritsuka by the arms. "Not even fighting back eh? What a slut" The leader took ritsuka by the legs and spread them apart.

"Wa-wait are you going to just go in, no prep!?" Shouted Ritsuka, alarmed for the wellbeing of his asshole.

"Someone please shut him up, i don't want to hear his whinings" another naked person came and forced open Ritsuka's mouth, promptly fulling it with his hard erection. "You better start working his dick you cocksucker".

Ritsuka did as ordered and started bobbing up and down on the foreing member invading his mouth, he was so focused that he didn't realise that the leader aligned his dick to his asshole, that is until it started making it's way inside him.

"mmmhp!" moaned Ritsuka in pain.

"You like this don't you? having your holes filled by cocks, why don't you make yourself useful and give those two a handjob" Once again Ritsuka did as ordered and grabbed the most close dicks into his hands and started masturbating them.

The dick on Ritsuka's ass iniciates to go in and out of him mercilessly making the brunnette to whimper, this is the moment that the dick inside his mouth ejaculates, Ritsuka, being caught off guard, tries to swallow what he can but ultimately some jizz gets out and dangles on his chin.

"You love that taste don't you bitch!" Said the leader as he thrusts his member as deep as he can inside Ritsuka, whose vocabulary has been limited to moans and wimps.

"Tell me you love it slut! Tell your master you want more cocks!" exclamed the leader as he rammed his meat in and out.

"I-i ne-need cocks ma-master, i lo-love them!" Shouted Ritsuka, as he came.

"Ha, you came before your master, bitch how dare you" Master slapped Ritsuka's butt strong enough to leave a mark.

"Ah, i am sorry Master, please use me whoever you want!" The dicks he was stroking came at that moment, coating his face with two loads of semen.

"Go on then, please more and more dicks with your body, i am sure it's the only thing you are capable at this point" Ritsuka didn't retort and even if he wanted to he couldn't as his mouth was being filled once again by a foreing manhood, his hands got busy as well with a new pair of members being stroked.

This went on for a while until the only Chaldea stuff remaining was the leader, the Master who now filled Ritsuka's ass with his cum.

"Zank u Masta" Said Ritsuka whose sexually overstimulated mind couldn't think right anymore.

"Look at you, the last master of chaldea" Said the Master as he took in the cum covered body of Ritsuka "What a joke, you are nothing more than a cock hungry slut" The Master spat on Ritsuka's face, action being returned by a giggle from Ritsuka.

Now, alone in his room laif the last master of humanity whose mind and body has succumbed to the carnal pleasures of humanity.

For humanity destroys itself the more humanity desires.

* * *

"And cut! That is how they say it in this times no?" Said Shakespeare turning to see Hans already writing something on his tablet and getting out of his room. "Mm? are we going to leave master like that? It might have been a little too much for him"

"Leave him, the only proof of what happened is Ritsuka and ourselves, the moment you completely undo your King's men is the moment we go to our workshops and start the hellish process of writing, besides if master can recover from witnessing the singularities i am sure this is nothing, now let's go already" Explained Hans, considering that he had obtainted enough data and leaved the room without waiting for Shakespeare.

"Humu, if you put it that way, well! It was a nice show master, until our path crosses again!" Shakespeare left the room and accompanied Hans.

They had a book to write afterall.

* * *

The next day Mash knocked on his senpai's door. 

**Notes for the Chapter:**

> Hey it's me, ya boy the writer who writes on and off, i wrote this instead of farming on GilFest or ShishouFest so... Yorokobe, i guess.
> 
> BTW i think i will do a Genderbend mash next chapter, maybe a paracelsus since i am using him a lot in GilFest, on another one i'll definetively do a blackbeard one where he crossdresses Ritsuka and does genderplay since in a dialogue in summer 3 he said something along the lines of "If i can imagine it's a woman it's ok*


End file.
